The present invention relates generally to internal combustion engines and, more particularly, to a cylinder liner insert to be cast-in-place in a light alloy, preferably aluminum, cylinder block, and a method of making a cylinder block with such a cylinder liner insert which comprises at least two generally cylindrical cylinder liners joined together along aligned portions thereof.
A continuing trend in the automotive industry is to reduce the size and weight of modern automobiles and to increase their efficiency in other ways due to fuel shortages and rising fuel costs. In many cases, weight reduction has been pursued by replacing metal components with lighter weight components made of plastics, ceramics or other lighter weight materials. The automobile engine is a major heavyweight component which has been both size reduced and constructed of lighter weight materials. Substantial engine weight reduction has been accomplished by casting the engine cylinder block of light weight alloys, preferably aluminum alloys, as opposed to cast iron.
While cast aluminum engine blocks provide significant engine weight reduction, the wear properties of the cylinder walls must match those of associated piston rings. Traditionally, machined cast iron cylinder liners are pressed into a precast aluminum engine block or preferably, such liners are placed in the block mold prior to casting such that the liners are cast-in-place in the aluminum engine block. In either event, successful operation of the block depends upon the rate at which heat can be extracted from the cylinders across the iron/aluminum interface, which in turn depends upon the contact area between the iron and aluminum.
The provision of individual cylinder liners in a cast-in-place process is illustrated in U.S. Pat. No. 4,446,906. The individual cylinder liners provide a good heat extraction rate since the aluminum is cast circumferentially around the iron liners and its contraction provides good contact with the liners for heat transfer; however, there are disadvantages. For example, the overall size of the engine is greater because space must be provided between cylinders for the core and the casting operation is made more complex due to the required handling of each of the individual cylinder liners.
There is thus a need for an improved cylinder liner and a method for producing a lightweight engine cylinder block by casting-in-place such a cylinder liner.